1. Technical Field
Exemplary embodiments of the present invention relate to an operational amplifier, and more particularly, to an operational amplifier having a high slew rate and stability, and a method of operating the operational amplifier.
2. Discussion of Related Art
The load capacitance and power consumption of a liquid crystal panel driving apparatus for driving a liquid crystal panel of a liquid crystal display increases as the resolution of the display increases. For example, the driving apparatus may be a source driver such as a data line driver. The increase in load capacitance greatly affects the slew rate and stability of an operational amplifier included in the liquid crystal driving apparatus. An operational amplifier operating at low power and low voltage may be used in the driving apparatus to reduce power consumption.
The slew rate of an operational amplifier is the maximum rate of change of the output voltage of the operational amplifier, which may be measured in, for example, volts per microseconds. The slew rate may be obtained by dividing the bias current (or tail current) of an input stage by a compensation capacitance. The slew rate may be increased by increasing the bias current (or tail current) of the input stage or by decreasing the compensation capacitance.
However, increases to the bias current cause static current increases, which increase the power consumed by the operational amplifier. Increasing the compensation capacitance may improve the stability of the operational amplifier. However, increasing the compensation capacitance also increases the layout size of the operational amplifier, which may decrease slew rate. Further, decreasing the compensation capacitance can increase the settling time of the operational amplifier.
Thus, there is a need for an operational amplifier having a smaller compensation capacitance and a lower static current, which can provide a faster slew rate, better stability, and a reduced power consumption.